Hi,

I think my car is burning too rich a mixture (checked the plugs today, they are buried in a layer of soot) and so is the exhaust. (also noticing loss of power and mileage)

Will resetting the ECU help? If so, do I just disconnect the battery terminal, leave it for an hour and reconnect it?

Also, some threads say that I have to leave the car to idle for 10 minutes for the ECU to re learn the a/f mixture

Is this right?

car is a 99 Accord EX 4 cyl.


Thanks,

Rao

 

you have to remove the ecu fuse in order to reset your ecu...otherwise disconnecting the battery will do nothing i believe...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nick H &raquo;</TD></TR><TR><TD CLASS="quote">you have to remove the ecu fuse in order to reset your ecu...otherwise disconnecting the battery will do nothing i believe...</TD></TR></TABLE>

where is this ecu everyone talks about??? please tell me its not on the ecu itself, that metal plates a biatch to get off

 

whens the last time you replaced the 02 sensor.........???

and YES, leaving the battery disconnected for a while WILL reset your ECU.......fuses get their power from the battery....so disc the batter is just likeing pulling the ecu fuse.......

make sure you let the car idle for a few minutes, so the ecu can relearn the idle

 

Hi,

My car is a 99 accord and has 69000 miles on it. I dont think the O2 sensor was ever replaced till date. I was also thinking if the sensor is bad... But how did it start exactly after the valve adjustment?

Thanks

es

 

Also, If I reset the ECU and it relearns the idle properly, does it mean that the O2 sensor is working fine? Coz it does seem to come back to idle properly at around 700 rpm.

 

Rich mixture could be your O2 sensor, and if you run it rich like that for too long you will ruin your cat.

O2 sensors ought to be replace at least every 100K miles, and some say 70K miles.

Its a good idea to keep track of your mileage for just this reason. If your mileage suddenly changes drastically, then you should look for an explanation, especially of you recently did a tuneup.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">Also, If I reset the ECU and it relearns the idle properly, does it mean that the O2 sensor is working fine? </TD></TR></TABLE>

nope.....if ur getting shitty gas milege, 99% of the time its bad O2 sensor......make sure ur plugs were not previously fouled, the dist. is still working fine.....if u reset the ECU and it dont help, id bet o2

 

Hi,

How do I check wether my distributor is working fine? And is there a way to check if the o2 sensor is good or bad?

Thanks

es

 

What MPG is your car getting? I have a similar problem. Read this thread
https://honda-tech.com/zerothread?id=817121

 

Hi,

I am getting around 21 - 22 in city + highway driving, used to be closer to 26..

Not as bad as yours, but how did your problem start in the first place? Mine started right after a valve adjustment.

Do you notice a loss in power/ acceleration also?

 

Hi,

I took the car to a honda service center today and had them hook it up to a diagnostic unit to see if there is a problem with the o2 sensor. There engine is not throwing any code, the o2 sensor seems to be giving voltages between .15 and .86 volts. The voltage seems to be oscillating around 3-4 times per second. How can I detect if the sensor is just sluggish?

One thing I noticed was that the ignition timing advance was around 10 degrees during idling (just out of spec of 11 - 13 degrees), and when the throttle is given, it goes up to around 14 - 15 degrees.

Isnt that a little less for this engine? I am not sure but it sounds too advanced. I am using premium fuel, but that should not advance it too much...

The diagnostic unit says that the Ignition advance is determined by the ECU... so why iis it setting it so low?

thanks

es